Frictionless inclined plane physics homework

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A 2.0 kg mass slides down a frictionless inclined plane at a 30-degree angle, starting from rest, and the goal is to determine its speed after sliding 3.0 m. The initial force calculation of 4.9 N was incorrect because the mass was not included in the force equation. The correct force should be calculated using F = mg sin(theta), which results in a different value. The work done on the mass, W = Fd, should also reflect this correction. The final speed calculation must incorporate the accurate force to yield the correct result.
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A 2.0 kg mass slides down a frictionless inclined plane that makes an angle of 30 degrees with the horizontal. The sass starts from rest. What is its speed after it has slid a distance of 3.0 m along the incline?

I got:

F = (sin30)(9.8)
F = 4.9 N

W = Fd
W = (4.9) (3) = 14.7 J

W = E_kin
14.7 J = 1/2 mv^2
v = 1.21 m/s

Is my method correct? I'm very unsure how to do this one. Thanks.
 
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your Work-Energy method is excellent ...
but a few chapters ago, F = M g sin (theta)
. . . if you had USED units [kg N/kg] you would have caught your error.
 
F = M g sin (theta) ?

I'm not sure what you mean. :confused:
 
you forgot the mass when you calculated the force.
 

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